The data processing and communication fields frequently require the use of multiple conductor cables to couple digital data and timing signals between subsystem components. Many such cables are terminated with multi conductor connectors to facilitate connecting and disconnecting various subsystem components.
For example, it is sometimes desirable to permit either of two computers to output data to a single printer. One way of accomplishing the selection of which computer will output data to the printer is to disconnect the cable coupling the non-selected computer to the printer, and reconnecting the cable from the selected computer to the printer. While this procedure is adequate for some purposes, it has certain disadvantages that make it somewhat inconvenient for some applications, and very inconvenient for others.
Because of the disadvantages of manually switching data cables, multi-conductor two-position switches are sometimes used to eliminate the requirement for physically connecting and disconnecting cables each time it is desired to change a cable coupling configuration. If the requirement is to couple either of two devices to another device by means of a switch, the switch is required to have at least two possible positions. Sometimes it is desirable to have a third or "off" switch position in which neither of the two input terminal ports of the switch are coupled to the output port. An off position is useful, for example, in permitting diagnostic testing or trouble shooting of the output device normally coupled to either of two input devices.
Although two-position switches for one and two conductors (referred to as SPDT or DPDT, for single-pole, double-throw and double-pole, double-throw respectively) are commonly available, switches capable of coupling greater numbers of conductors become increasingly expensive.
The problem of obtaining two or three position switches for data communication is aggravated by the fact that typical data processing interconnecting cables contain many conductors. For example the widely used Electronic Industries Association (EIA) RS-232-C Standard specifies use of 25-pin connectors. Presently available switches capable of connecting either of two 25-pin cables to a common output cable are both large and costly.
The present invention employs a pivotable printed circuit edge connector array design to permit construction of a low cost, two or three position multi-pole switch that is easily adaptable to interconnecting large numbers of conductors. An alternate embodiment affords more than two active switch positions. The invention also employs a diagonal contact wiping action to overcome two problems associated with the switching of low level analog or digital switches. The two problems are:
(1) The inability of low power signals to burn away oxidation or other contamination layers on switch contacts and
(2) The development of high resistance interface points between low power switching contacts that have remained in one position for a long time.